The present disclosure relates to a machine tool, particularly a grinding machine, comprising a workpiece mount, a tool unit, a measuring device and a control device which is connectable to the measuring device and the tool unit. The present disclosure further relates to a method for measuring a workpiece in a machine tool, particularly a grinding machine. The present disclosure further relates to a computer readable non-transitory storage medium.
Machine tools, particularly grinding machines, are known in the art. By way of example, cylindrical grinding machines may comprise rotationally symmetric tools, particularly grinding wheels, which may cooperate in a suitable fashion with a workpiece for material removal. By way of example, cylindrical grinding machines may be arranged for external cylindrical grinding, internal cylindrical grinding or for infeed grinding and angular infeed grinding, respectively. Besides grinding wheels generally also abrasive belts may be utilized for cylindrical grinding. Besides rotationally symmetric surfaces, also eccentrically shaped workpiece surfaces may be machined when the workpiece mount and the tool unit are appropriately drivable and movable with respect to each other. In this way, for instance, camshafts, crankshafts or similar workpieces comprising eccentric geometries may be machined and/or grinded.
A to-be-machined workpiece may be received between two centers of a workpiece mount, for instance, or may be one-sidedly received at a workpiece mount. Besides, so-called centerless grinding is known which involves that the workpiece is not received between centers of the grinding machine, but rather received and guided via receiving bars, regulating wheels, guiding rollers and the like for instance.
A grinding machine is known from DE 10 2009 042 252 A1 which grinding machine comprises a measurement apparatus that is arranged for in-process measuring test pieces in the course of a machining process. To this end, the measurement apparatus comprises a measurement head which is pivotably connected with a base body of the measurement apparatus via a linkage. The measurement head comprises a deflectable measuring probe which is coupled to a measuring prism, and which is provided for determining the diameter or the roundness of the test piece. The linkage shall be arranged to track movements of the test piece, at least in a defined region, for instance a rotation of a crank pin of a crankshaft about the rotation axis of the crankshaft.
In this way, also with grinding machining processes of eccentrically arranged cylinder surfaces basically an in-process measurement may be effected, at least sectionally. This may take place simultaneously to the grinding machining. However, the measurement apparatus comprises a complex structure. The linkage is arranged in a complex fashion and needs to be controlled in an elaborate fashion when in operation.
The so-called in-process measurement, i.e. a measurement in the course of a machining operation, may enable high precision machining operations, and may contribute to an increased manufacturing quality and process reliability. To this end, it is however regularly required to provide a measurement head which is accurately adapted to the expected measure for each to-be-measured workpiece dimension, i.e. for each diameter, for instance. This may involve a single purpose measurement head, or a measurement head at which for instance two measuring probes are received in an adjustable fashion and that comprise a distance to one another which corresponds to the expected distance. The measuring probes have to be adjusted in a high precision fashion and respectively oriented with respect to the respected to-be-inspected measure.
Such an in-process measurement head is shown for instance in DE 196 16 353 A1. In this respect, effortful setting, adjusting and/or calibrating processes which may be required to adapt the measurement head to the respective intended purpose may be disadvantageous. Particularly, with single-piece machining, small batch series and medium batch series, for instance setting the measurement head may cause a time consumption which is not negligible.
In this context, it is worth mentioning that the measurement apparatus which is known from DE 10 2009 042 252 A1, in some circumstances, may not correspond to the measurement accuracy which is necessary for in-process measurements. The associated measurement head comprises a measuring probe and a measuring prism which are coupled via a plurality of linkage elements of the linkage with an absolute measurement reference. Any deviations of single elements of the kinematic chain of the linkage may be reflected in the location of the of the measurement head with respect to the test piece. This may be particularly disadvantageous when measuring eccentrically shaped workpieces in a section-by-section fashion. The location of the measurement head with respect to the test piece, for instance with respect to its angular position, may be error prone.
In view of this, it is an object of the present disclosure to provide a machine tool, particularly a grinding machine, which enables a high-precision measuring of workpieces with little efforts, particularly for measuring workpiece diameters.
It is a further object to provide a machine tool, particularly a grinding machine, which enables a highly flexible measuring of workpieces with little efforts.
It is a further object to provide a corresponding method for measuring a workpiece, particularly for measuring workpiece diameters.
It is still a further object to provide a corresponding machine tool control program disposed on a computer readable non-transitory storage medium.